This disclosure generally relates to aircraft fuselage configurations and cabin layouts, and deals more particularly with aircraft fuselage configurations and cabin layouts for multi-deck aircraft having an upper passenger seating deck.
The profitability of an airline is directly related to the number of passengers and the amount of cargo-carrying space its planes are equipped to transport. The greater the passenger seating space, the greater the potential passenger revenues. Similarly, the greater the cargo-carrying space, the greater are the potential cargo revenues. Therefore, an airline can increase its profitability by increasing passenger seating space and cargo-carrying capability.
One method of increasing aircraft passenger seating and cargo space is to increase the length of the aircraft's fuselage. This process is commonly known as “stretching”. There are a number of problems associated with stretching an aircraft, including a reduction in the aft body rotation clearance, disproportionate growth of the lower cargo space, a reduction in aircraft maneuverability in and around airports, and a reduction in the ability to park the aircraft in length-constrained airport gates.
A second method of increasing passenger space is to use a full-length main seating deck and an additional upper seating deck provided over the entire length of the fuselage, over a forward portion of the fuselage, or over an aft portion of the fuselage. Increasing passenger space by use of a forward, an aft, or a full upper deck is generally preferred to stretching an aircraft because the resulting aircraft is easier to maneuver at airports and is capable of larger rotation angles during takeoff and landing. Such a craft also has reduced fuselage wetted area per seat and hence reduced skin friction drag on a per seat basis.
There are a number of problems associated with attempting to design a viable full upper deck aircraft. One problem is that dual-deck aircraft have a fuselage perimeter and a fuselage wetted area which are non-optimal. Thus, full upper deck configurations typically suffer from relatively high levels of profile drag. As used herein, the term “profile drag” means the sum of form drag and skin friction drag.
In one design aspect, it is generally accepted that aircraft weight (without payload) and aerodynamic drag correlate with aircraft fuselage surface area and correspondingly with aircraft cross sectional perimeter. It is desirable to reduce both weight and aerodynamic drag because greater aircraft weight and/or drag reduces payload and/or range, and higher aerodynamic drag in flight translates into higher fuel usage, and also translates into higher carbon dioxide emissions, all other factors being equal. Aerodynamic drag increases as the lateral cross-sectional area increases because perimeter is related directly to cross-sectional area for a fuselage shape. However, the larger the aircraft lateral cross-sectional area, the more spacious the interior of the aircraft for passenger comfort. Accordingly, a balance must be struck between interior space (which translates to cross-sectional area) on the one hand and weight and aerodynamic drag on the other. With increasing fuel costs, reduction in aircraft fuselage perimeter and cross-sectional area is becoming more desirable.
There is a need for improved fuselage designs that substantially increase passenger seating capacity relative to traditional single-passenger-deck configurations, while minimizing fuselage perimeter and fuselage wetted area relative to double-passenger-deck configurations.